Soft absorbent tissue containing derivitized amino-functional polysiloxanes

ABSTRACT

A tissue product having improved hand feel and good wettability is produced by printing onto one or both sides of the tissue an aqueous emulsion containing a derivitized amino-functional polysiloxane. The derivitized amino-functional polysiloxane structure has one or more pendant groups containing an amine derivative.

BACKGROUND OF THE INVENTION

In the field of soft tissues, such as facial tissue and bath tissue, itis well known that the application of polysiloxanes to the surface ofthe tissue can impart an improved surface feel to the tissue. However,polysiloxanes are also known to impart hydrophobicity to the treatedtissue. Hence, it is difficult to find a proper balance between softnessand wettability, both of which are desirable attributes for tissue,particularly bath tissue.

SUMMARY OF THE INVENTION

It has now been discovered that the wettability of a tissue can beimproved with minimal negative impact on the surface feel of the tissueby treating one or both outer surfaces of the tissue with a particulargroup of derivitized amino-functional polysiloxanes. More specifically,suitable polysiloxane structures have one or more pendant groups whichcontain an amine derivative. A general structure is as follows:

wherein:

“A” is selected from the group consisting of hydroxy; C₁-C₆ alkylradical; or C1-C6 alkoxyl radical, which can be straight chain, branchedor cyclic, unsubstituted or substituted; or a “B”.

R₁=a C₁-C₆ alkyl radical, which can be straight chain, branched orcyclic;

G=(R₁)_(m)+(B)_(p)+(D)_(q) with R₁, B and D distributed in random orblock fashion;

m=20-100,000;

p=1-5,000;

q=0-5,000;

m+p+q=n;

B=—(R₃—N—R₄)—R₅—W

wherein

t=0 or 1;

R₃=a C₂-C₈ alkylene diradical, which can be straight chain or branched,substituted or unsubstituted;

R₄=a hydrogen or C₁-C₈ alkyl radical, which can be straight chain orbranched, substituted or unsubstituted or a R₆;

R₅=a C₂-C₈ alkylene diradical, which can be straight chain or branched,substituted or unsubstituted;

W=—N—R₆R₇; OCONR_(q)R₁₀;

wherein

R₆=a radical of hydrogen, COOR₈, or CONR₉R₁₀;

R₇=a radical COOR₈, or CONR₉R₁₀;

R₈=a C₁-C₁₀ alkyl radical, which can be straight chain, branched orcyclic, substituted or unsubstituted, aliphatic or aromatic;

R₉=hydrogen or a C₁-C₁₀ alkyl radical, which can be straight chain,branched or cyclic, substituted or unsubstituted, aliphatic or aromatic;

R₁₀=hydrogen or a C₁-C₁₀ alkyl radical, which can be straight chain,branched or cyclic, substituted or unsubstituted, aliphatic or aromatic;

D=—R₁₁—Y,

wherein

R₁₁=a C₂-C₆ alkylene diradical;

Y=—NR₁₂R₁₃, —OSO₃R₁₄, or —[N⁺R₁₄R₁₆SO₂PhR₁₅]I⁻ where Ph is a phenylradical;

wherein

R₁₂=hydrogen, C₁-C₈ alkyl, —COOR₁₆, or —CONR₁₇R₁₈ radical;

R₁₃=hydrogen, C₁-C₈ alkyl, COOR₁₆, or —CONR₁₇R₁₈ radical;

R₁₄=C₁-C₈ alkyl radical, which can be aromatic, aliphatic, cyclic,straight chain or branched;

R₁₅=C₁-C₂₄ alkyl radical;

R₁₆=C₁-C₈ alkyl radical, which can be aromatic, aliphatic, cyclic,straight chain or branched;

R₁₇=C₁-C₈ alkyl radical, which can be aromatic, aliphatic, cyclic,straight chain or branched;

R₁₈=C₁-C₈ alkyl radical, which can be aromatic, aliphatic, cyclic,straight chain or branched; and

I=a halide or sulfate ion.

Representative species within the foregoing general structure includethe following wherein the foregoing definitions apply:

The derivitized amino-functional polydimethylsiloxanes described abovecan be applied to the tissue web alone or in conjunction with otherchemicals, such as bonders or debonders. They can be applied to thetissue web, particularly an uncreped through-dried web, by spraying orprinting. Rotogravure printing of an aqueous emulsion is particularlyeffective. Add-on amounts can be from about 0.5 to about 15 dry weightpercent, based on the weight of the tissue, more specifically from about1 to about 10 dry weight percent, still more specifically from about 1to about 5 weight percent, still more specifically from about 2 to about5 weight percent. The distribution of the deposits of the derivitizedamino-functional polydimethylsiloxanes is substantially uniform over theprinted surface of the tissue, even though the surface of the tissue,such as in the case of uncreped throughdried tissues, may be highlytextured and three-dimensional.

The Wet Out Time (hereinafter defined) for tissues of this invention canbe about 15 seconds or less, more specifically about 10 seconds or less,still more specifically about 6 seconds or less, still more specificallyabout 5 seconds or less, still more specifically from about 4 to about 8seconds. As used herein, “Wet Out Time” is related to absorbency and isthe time it takes for a given sample to completely wet out when placedin water. More specifically, the Wet Out Time is determined by cutting20 sheets of the tissue sample into 2.5 inch squares. The number ofsheets used in the test is independent of the number of plies per sheetof product. The 20 square sheets are stacked together and stapled ateach corner to form a pad. The pad is held close to the surface of aconstant temperature distilled water bath (23 +/−2° C.), which is theappropriate size and depth to ensure the saturated specimen does notcontact the bottom of the container and the top surface of the water atthe same time, and dropped flat onto the water surface, staple pointsdown. The time taken for the pad to become completely saturated,measured in seconds, is the Wet Out Time for the sample and representsthe absorbent rate of the tissue. Increases in the Wet Out Timerepresent a decrease in absorbent rate.

The “Differential Wet Out Time” is the difference between the Wet OutTimes of a tissue sample treated with a derivitized amino-functionalpolydimethylsiloxane and a control tissue sample which has not beentreated. The Differential Wet Out Time, for purposes of this invention,can be about 10 seconds or less, more specifically about 5 seconds orless, still more specifically about 3 seconds or less, still morespecifically about 2 seconds or less, and still more specifically about1 second or less.

The ratio of the Differential Wet Out Time to the add-on amount of thederivitized amino-functional polydimethylsiloxane can be about 3 secondsper weight percent or less, more specifically about 1 second per weightpercent or less, still more specifically about 0.5 second per weightpercent or less.

Tissue sheets useful for purposes of this invention can be creped oruncreped. Such tissue sheets can be used for facial tissues, bathtissues or towels. They can have one, two, three or more plies. Thebasis weight of the tissue product can be from about 25 to about 50grams per square meter. If used for bath tissue, a single ply tissuehaving a basis weight of from about 30-40 grams per square meter isparticularly suitable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an uncreped throughdried process formaking bath tissue in accordance with this invention.

FIG. 2 is a schematic diagram of the post-manufacturing method ofhandling the uncreped throughdried web and the rotogravure coatingprocess used to apply the derivitized amino-functionalpolydimethylsiloxane emulsion in accordance with this invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIG. 1, shown is a schematic flow diagram of a throughdrying process for making uncreped throughdried tissue sheets. Shown isthe headbox 1 which deposits an aqueous suspension of papermaking fibersonto an inner forming fabric 3 as it traverses the forming roll 4. Outerforming fabric 5 serves to contain the web while it passes over theforming roll and sheds some of the water. The wet web 6 is thentransferred from the inner forming fabric to a wet end transfer fabric 8with the aid of a vacuum transfer shoe 9. This transfer is preferablycarried out with the transfer fabric traveling at a slower speed thanthe forming fabric (rush transfer) to impart stretch into the finaltissue sheet. The wet web is then transferred to the throughdryingfabric 11 with the assistance of a vacuum transfer roll 12. Thethroughdrying fabric carries the web over the throughdryer 13, whichblows hot air through the web to dry it while preserving bulk. There canbe more than one throughdryer in series (not shown), depending on thespeed and the dryer capacity. The dried tissue sheet 15 is thentransferred to a first dry end transfer fabric 16 with the aid of vacuumtransfer roll 17. The tissue sheet shortly after transfer is sandwichedbetween the first dry end transfer fabric and the transfer belt 18 topositively control the sheet path. The air permeability of the transferbelt is lower than that of the first dry end transfer fabric, causingthe sheet to naturally adhere to the transfer belt. At the point ofseparation, the sheet follows the transfer belt due to vacuum action.Suitable low air permeability fabrics for use as transfer belts include,without limitation, COFPA Mononap NP 50 dryer felt (air permeability ofabout 50 cubic feet per minute per square foot) and Asten 960C(impermeable to air). The transfer belt passes over two winding drums 21and 22 before returning to pick up the dried tissue sheet again. Thesheet is transferred to the parent roll 25 at a point between the twowinding drums. The parent roll is wound onto a reel spool 26, which isdriven by a center drive motor.

Particularly suitable methods of producing uncreped throughdriedbasesheets for purposes of this invention are described in U.S. Pat. No.6,017,417 issued Jan. 25, 2000 to Wendt et al. and U.S. Pat. No.5,944,273 issued Aug. 31, 1999 to Lin et al., both of which are hereinincorporated by reference.

FIG. 2 illustrates a suitable method for applying the derivitizedamino-functional polydimethylsiloxane to the tissue basesheet. Shown isthe parent roll 25 being unwound and passed through two calender nipsbetween calender rolls 30 a and 31 a and 30 b and 31 b. The calenderedweb is then passed to the rotogravure coating station comprising a firstclosed doctor chamber 33 containing the hydrophilically-modifiedamino-functional polydimethylsiloxane emulsion to be applied to a firstside of the web, a first engraved steel gravure roll 34, a first rubberbacking roll 35, a second rubber backing roll 36, a second engravedsteel gravure roll 37 and a second closed doctor chamber 38 containingthe derivitized amino-functional polydimethylsiloxane emulsion to beapplied to the second side of the web. If both sides of the web are tobe treated, the two emulsions can be the same or different. Thecalendered web passes through a fixed-gap nip between the two rubberbacking rolls where the derivitized amino-functionalpolydimethylsiloxane emulsion is applied to the web. The treated web isthen passed to the rewinder where the web is wound onto logs 40 and slitinto rolls of bath tissue.

EXAMPLES Example 1

In order to further illustrate this invention, an uncreped throughdriedtissue is produced using the methods described in FIGS. 1 and 2 andtreated with a derivitized amino-functional polydimethylsiloxane as setforth in structure (4) described herein above.

More specifically, a single-ply, three-layered uncreped throughdriedbath tissue is made using eucalyptus fibers for the outer layers andsoftwood fibers for the inner layer. Prior to pulping, a quaternaryammonium softening agent (C-6027 from Goldschmidt Corp.) is added at adosage of 4.1 kg/Mton of active chemical per metric ton of fiber to theeucalyptus furnish. After allowing 20 minutes of mixing time, the slurryis dewatered using a belt press to approximately 32% consistency. Thefiltrate from the dewatering process is either sewered or used as pulpermake-up water for subsequent fiber batches but not sent forward in thestock preparation or tissue making process. The thickened pulpcontaining the debonder is subsequently re-dispersed in water and usedas the outer layer furnishes in the tissuemaking process.

The softwood fibers are pulped for 30 minutes at 4 percent consistencyand diluted to 3.2 percent consistency after pulping, while the debondedeucalyptus fibers are diluted to 2 percent consistency. The overalllayered sheet weight is split 30%/40%/30% among the eucalyptus/refinedsoftwood/eucalyptus layers. The center layer is refined to levelsrequired to achieve target strength values, while the outer layersprovided the surface softness and bulk. Parez 631NC is added to thecenter layer at 2-4 kilograms per tonne of pulp based on the centerlayer.

A three layer headbox is used to form the wet web with the refinednorthern softwood kraft stock in the two center layers of the headbox toproduce a single center layer for the three-layered product described.Turbulence-generating inserts recessed about 3 inches (75 millimeters)from the slice and layer dividers extending about 1 inch (25.4millimeters) beyond the slice are employed. The net slice opening isabout 0.9 inch (23 millimeters) and water flows in all four headboxlayers are comparable. The consistency of the stock fed to the headboxis about 0.09 weight percent.

The resulting three-layered sheet is formed on a twin-wire, suction formroll, former with the two forming fabrics being a Lindsay 2164 and anAsten 867a fabric. The speed of the forming fabrics is 11.9 meters persecond. The newly-formed web is then dewatered to a consistency of about20-27 percent using vacuum suction from below the forming fabric beforebeing transferred to the transfer fabric, which is travelling at 9.1meters per second (30% rush transfer). The transfer fabric is anAppleton Wire T807-1. A vacuum shoe pulling about 6-15 inches (150-380millimeters) of mercury vacuum is used to transfer the web to thetransfer fabric.

The web is then transferred to a throughdrying fabric (Lindsay WireT1205-1). The throughdrying fabric is travelling at a speed of about 9.1meters per second. The web is carried over a Honeycomb throughdryeroperating at a temperature of about 350° F. (175° C.) and dried to finaldryness of about 94-98 percent consistency. The resulting uncrepedtissue sheet is then wound into a parent roll.

The parent roll is then unwound and the web is calendered twice. At thefirst station the web is calendered between a steel roll and a rubbercovered roll having a 4 P&J hardness. The calender loading is about 90pounds per lineal inch (pli). At the second calendering station, the webis calendered between a steel roll and a rubber covered roll having a 40P&J hardness. The calender loading is about 140 pli. The thickness ofthe rubber covers is about 0.725 inch (1.84 centimeters).

The calendered single-ply web is then fed into the rubber-rubber nip ofthe rotogravure coater to apply the derivitized amino-functionalpolydimethylsiloxane (structure (4)) emulsion to both sides of the web.The aqueous emulsion contains 40% of a derivitized aminopolydimethylsiloxane, 8% surfactant, 0.5% antifoaming agent, 0.2%preservative, and the balance water. The gravure rolls areelectronically engraved, chrome over copper rolls supplied by SpecialtySystems, Inc., Louisville, Ky. The rolls have a line screen of 200 cellsper lineal inch and a volume of 6.0 Billion Cubic Microns (BCM) persquare inch of roll surface. Typical cell dimensions for this roll are140 microns in width and 33 microns in depth using a 130 degreeengraving stylus. The rubber backing offset applicator rolls are a 75Shore A durometer cast polyurethane supplied by American Roller Company,Union Grove, Wis. The process is set up to a condition having 0.375 inchinterference between the gravure rolls and the rubber backing rolls and0.003 inch clearance between the facing rubber backing rolls. Thesimultaneous offset/offset gravure printer is run at a speed of 2000feet per minute using gravure roll speed adjustment (differential) tometer the polysiloxane emulsion to obtain the desired addition rate. Thegravure roll speed differential used for this example is 1000 feet perminute. This process yields an add-on level of 2.5 weight percent totaladd-on based on the weight of the tissue. The tissue is then convertedinto bath tissue rolls. Sheets from the bath tissue rolls have a silky,lotiony hand feel and a Wet Out Time of 5.5 seconds. (Similarly madetissues without the treatment of this invention had a Wet Out Time ofabout 4.0 seconds.) The ratio of the differential Wet Out Time to theweight percent add-on amount is 0.6.

Example 2

An uncreped throughdried tissue is made substantially as described abovewith the following exceptions: (1) the overall layered weight is split30%/40%/30% among the eucalyptus/refined softwood/eucalyptus layers; (2)no Parez is added to the center layer; (3) the add-on level of thederivitized amino-functional polydimethylsiloxane is 2.5 weight percent;(4) the structure of the hydrophilically-modified amino-functionalpolydimethylsiloxane is as set forth in structure (6) herein above; and(5) the derivitized amino-functional polydimethylsiloxane constitutes 30weight percent of the aqueous emulsion used to deliver the derivitizedamino-functional polydimethylsiloxane to the tissue. The resulting bathtissue product obtained has a silky, lotiony hand feel and a Wet OutTime of 6 seconds.

Example 3

An uncreped throughdried tissue is produced similarly as described inExample 1 with the following exceptions: (1) prior to pulping, apolydimethylsiloxane of structure (8) is added to the eucalyptus fibersat a dosage of 0.2 kg/Mton of active chemical per metric ton of fiber;(2) the add-on level of the derivitized amino-functionalpolydimethylsiloxane is 1.5 weight percent; (3) the structure of thederivitized amino-functional polydimethylsiloxane printed onto thetissue is as set forth in structure 14 herein above; and (4) thederivitized amino-functional polydimethylsiloxane constitutes 20 weightpercent of the aqueous emulsion used to deliver the derivitizedamino-functional polydimethylsiloxane to the tissue. The resulting bathtissue product obtained has a silky, lotiony hand feel and a Wet OutTime of 7 seconds.

It will be appreciated that the foregoing example and discussion is forpurposes of illustration only and is not to be construed as limiting thescope of this invention, which is defined by the following claims andall equivalents thereto.

I claim:
 1. A tissue having a Wet Out Time of about 15 seconds or lessand containing at least about 2 dry weight percent of ahydrophilically-modified amino-functional polysiloxane having thefollowing structure:

wherein: “A” is selected from the group consisting of hydroxy; C₁-C₆alkyl radical; or C1-C6 alkoxyl radical, which can be straight chain,branched or cyclic, unsubstituted or substituted; or a “B”. R₁=a C₁-C₆alkyl radical, which can be straight chain, branched or cyclic;G=(R₁)_(m)+(B)_(p)+(D)_(q) with R₁, B and D distributed in random orblock fashion; m=20-100,000; p=1-5,000; q=0-5,000; m+p+q=n;B=—(R₃—N—R₄)_(t)—R₅—W wherein t=0 or 1; R₃=a C₂-C₈ alkylene diradical,which can be straight chain or branched, substituted or unsubstituted;R₄=a hydrogen or C₁-C₈ alkyl radical, which can be straight chain orbranched, substituted or unsubstituted or a R₆; R₅=a C₂-C₈ alkylenediradical, which can be straight chain or branched, substituted orunsubstituted; W=—N—R₆R₇; OCONR₉R₁₀; wherein R₆=a radical of hydrogen,COOR₈, or CONR₉R₁₀; R₇=a radical COOR₈, or CONR₉R₁₀; R₈=a C₁-C₁₀ alkylradical, which can be straight chain, branched or cyclic, substituted orunsubstituted, aliphatic or aromatic; R₉=hydrogen or a C₁-C₁₀ alkylradical, which can be straight chain, branched or cyclic, substituted orunsubstituted, aliphatic or aromatic; R₁₀=hydrogen or a C₁-C₁₀ alkylradical, which can be straight chain, branched or cyclic, substituted orunsubstituted, aliphatic or aromatic; D=—R₁₁—Y, wherein R₁₁=a C₂-C₆alkylene diradical; Y=—NR₁₂R₁₃, —OSO₃R₁₄, or —[N⁺R₁₄R₁₆SO₂PhR₁₅]I⁻ wherePh is a phenyl radical; wherein R₁₂=hydrogen, C₁-C₈ alkyl, COOR₁₆, or—CONR₁₇R₁₈ radical; R₁₃=hydrogen, C₁-C₈ alkyl, COOR₁₆, or —CONR₁₇R₁₈radical; R₁₄=C₁-C₈ alkyl radical, which can be aromatic, aliphatic,cyclic, straight chain or branched; R₁₅=C₁-C₂₄ alkyl radical; R₁₆=C₁-C₈alkyl radical, which can be aromatic, aliphatic, cyclic, straight chainor branched; R₁₇=C₁-C₈ alkyl radical, which can be aromatic, aliphatic,cyclic, straight chain or branched; R₁₈=C₁-C₈ alkyl radical, which canbe aromatic, aliphatic, cyclic, straight chain or branched; and I=ahalide or sulfate ion.
 2. The tissue of claim 1 wherein the Wet Out Timeis about 10 seconds or less.
 3. The tissue of claim 1 wherein the WetOut Time is about 7 seconds or less.
 4. The tissue of claim 1 whereinthe Wet Out Time is about 5 seconds or less.
 5. The tissue of claim 1wherein the Wet Out Time is from about 4 to about 8 seconds.
 6. Thetissue of claim 1 having from about 0.5 to about 15 dry weight percentof the derivitized amino-functional polysiloxane.
 7. The tissue of claim1 having from about 1 to about 10 dry weight percent of the derivitizedamino-functional polysiloxane.
 8. The tissue of claim 1 having fromabout 1 to about 5 dry weight percent of the derivitizedamino-functional polysiloxane.
 9. The tissue of claim 1 having fromabout 2 to about 5 dry weight percent of the derivitizedamino-functional polysiloxane.
 10. The tissue of claim 1 wherein theratio of the Differential Wet Out Time to the add-on amount of thederivitized amino-functional polysiloxane is about 3 seconds per weightpercent or less.
 11. The tissue of claim 1 wherein the ratio of theDifferential Wet Out Time to the add-on amount of the derivitizedamino-functional polysiloxane is about 1 second per weight percent orless.
 12. The tissue of claim 1 wherein the ratio of the DifferentialWet Out Time to the add-on amount of the derivitized amino-functionalpolysiloxane is about 0.5 second per weight percent or less.
 13. Thetissue of claim 1 wherein the tissue is an uncreped throughdried tissue.14. The tissue of claim 1 wherein both sides of the tissue are printedwith the same derivitized amino-functional polysiloxane.
 15. The tissueof claim 1 wherein the derivitized amino-functional polysiloxane printedon one side of the tissue is different than the derivitizedamino-functional polysiloxane printed on the other side of the tissue.16. The tissue of claim 1 wherein W=NR₆R₇.
 17. The tissue of claim 1wherein W=OCONR₉R₁₀.
 18. The tissue of claim 1 wherein A=B.
 19. Thetissue of claim 1 wherein q=0.
 20. The tissue of claim 1 wherein(R₆=R₇=COOR₈).
 21. The tissue of claim 1 wherein (R₆=R₇=CONR₉R₁₀). 22.The tissue of claim 1 wherein the derivitized amino-functionalpolysiloxane has the following structure:


23. The tissue of claim 1 wherein the derivitized amino-functionalpolysiloxane has the following structure:


24. The tissue of claim 1 wherein the derivitized amino-functionalpolysiloxane has the following structure:


25. The tissue of claim 1 wherein the derivitized amino-functionalpolysiloxane has the following structure:


26. The tissue of claim 1 wherein the derivitized amino-functionalpolysiloxane has the following structure:


27. The tissue of claim 1 wherein the derivitized amino-functionalpolysiloxane has the following structure:


28. The tissue of claim 1 wherein the derivitized amino-functionalpolysiloxane has the following structure:


29. The tissue of claim 1 wherein the derivitized amino-functionalpolysiloxane has the following structure:


30. The tissue of claim 1 wherein the derivitized amino-functionalpolysiloxane has the following structure:


31. The tissue of claim 1 wherein the derivitized amino-functionalpolysiloxane has the following structure:


32. The tissue of claim 1 wherein the derivitized amino-functionalpolysiloxane has the following structure: